PSI - Issue 68

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Procedia Structural Integrity 68 (2025) 1280–1286 Structural Integrity Procedia 00 (2024) 000–000 Structural Integrity Procedia 00 (2024) 000–000

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European Conference on Fracture 2024 Obtaining traction-separation laws of adhesive joints using optical fiber strain measurements - Part A (Mode I) LeaAydin a , Stephan Marzi a, ∗ a Institute of Mechanics and Materials, Technische Hochschule Mittelhessen, Wiesenstraße 14, 35390 Gießen, Germany Abstract This work presents a new method for obtaining traction-separation laws (TSLs) from double cantilever beam (DCB) tests in mode I of adhesively bonded joints. Thereby a structural adhesive was used. The focus is on the applicability of an optical fiber sensor using beam theory and its comparison with more or less conventional methods. The optical fiber, attached along the length of the sample, allows real-time measurement of strain with high spatial resolution on the adherent throughout the test. This newly introduced technique provides information on crack-tip position and traction-separation relationships in the context of cohesive zone modeling (CZM). These data have been shown to provide rich evaluation possibilities. Additional measurements with force and position sensors, as well as rotary encoders, support the determination of the J-integral. With the help of these measurements, a good amount of information is available to apply various methods to evaluate a single experiment. Geisel and Marzi (2024) were also able to show in part B of this paper that this method can also be applied to mode III and achieved comparably good results. © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ECF24 organizers. Keywords: Adhesive joints; Optical fiber measurement; Fracture mechanics; Traction-separation law European Conference on Fracture 2024 Obtaining traction-separation laws of adhesive joints using optical fiber strain measurements - Part A (Mode I) LeaAydin a , Stephan Marzi a, ∗ a Institute of Mechanics and Materials, Technische Hochschule Mittelhessen, Wiesenstraße 14, 35390 Gießen, Germany Abstract This work presents a new method for obtaining traction-separation laws (TSLs) from double cantilever beam (DCB) tests in mode I of adhesively bonded joints. Thereby a structural adhesive was used. The focus is on the applicability of an optical fiber sensor using beam theory and its comparison with more or less conventional methods. The optical fiber, attached along the length of the sample, allows real-time measurement of strain with high spatial resolution on the adherent throughout the test. This newly introduced technique provides information on crack-tip position and traction-separation relationships in the context of cohesive zone modeling (CZM). These data have been shown to provide rich evaluation possibilities. Additional measurements with force and position sensors, as well as rotary encoders, support the determination of the J-integral. With the help of these measurements, a good amount of information is available to apply various methods to evaluate a single experiment. Geisel and Marzi (2024) were also able to show in part B of this paper that this method can also be applied to mode III and achieved comparably good results. © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ECF24 organizers. Keywords: Adhesive joints; Optical fiber measurement; Fracture mechanics; Traction-separation law © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers In the field of fracture mechanics, cohesive zone models, which represent a particular approach to predicting the failure of adhesive joints, require TSLs as input data. Campilho et al. (2013) have provided a comprehensive overview of di ff erent shapes and applications. For the case of peel failure investigated in this paper, the use of beams bonded with an adhesive layer is considered suitable. These beams are then loaded in mode I and the fracture behavior and crack growth, respectively, of the adhesive layer is monitored. These results allow the use of simulation models that reflect the behavior of the adhesive, for example in the event of a crash, without having to carry out time-consuming and expensive tests. The commonly used methods for the experimental evaluation of parameters necessary for the determination of such TSLs describe the traction-separation relationship of an adhesive at the initial crack tip. This makes it possible to obtain a prediction of the cohesive strength. However, this often requires a large number of valid In the field of fracture mechanics, cohesive zone models, which represent a particular approach to predicting the failure of adhesive joints, require TSLs as input data. Campilho et al. (2013) have provided a comprehensive overview of di ff erent shapes and applications. For the case of peel failure investigated in this paper, the use of beams bonded with an adhesive layer is considered suitable. These beams are then loaded in mode I and the fracture behavior and crack growth, respectively, of the adhesive layer is monitored. These results allow the use of simulation models that reflect the behavior of the adhesive, for example in the event of a crash, without having to carry out time-consuming and expensive tests. The commonly used methods for the experimental evaluation of parameters necessary for the determination of such TSLs describe the traction-separation relationship of an adhesive at the initial crack tip. This makes it possible to obtain a prediction of the cohesive strength. However, this often requires a large number of valid 1. Introduction 1. Introduction

∗ Corresponding author. Tel.: + 49-641-309-2124 E-mail address: stephan.marzi@me.thm.de ∗ Corresponding author. Tel.: + 49-641-309-2124 E-mail address: stephan.marzi@me.thm.de

2452-3216 © 2025 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of ECF24 organizers 10.1016/j.prostr.2025.06.199 2210-7843 © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ECF24 organizers. 2210-7843 © 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http: // creativecommons.org / licenses / by-nc-nd / 4.0 / ) Peer-review under responsibility of ECF24 organizers.